Process for the fractionation of whey constituents

ABSTRACT

A process for fractionation of dairy whey is described which enables various whey constituents, in particular, alpha-lactalbumin and beta-lactoglobulin, to be recovered in substantially pure form. Lactose may also be recovered. The mineral content of raw whey is reduced so that the calcium content is less than 120 parts per million. Thereafter, the whey is treated to allow the lactose to crystallize out for removal and selectively to flocculate the alpha-lactalbumin, leaving a liquor containing substantially pure beta-lactoglobulin.

This invention relates to the recovery of protein and other productsfrom whey and in particular to the fractionation of alpha-lactalbuminand beta-lactoglobulin from whey.

Whey is an aqueous run-off product in the manufacture of certain dairyproducts, such as cheese and caseins. In addition to a portion of dairyfat, the whey contains proteins, lactose and minerals. The predominantproteins in the whey are alpha-lactalbumin and beta-lactoglobulin. Thesecomponents are economically valuable in their own right and inparticular when recovered in partially or substantially purified form.

One process known for the treatment of whey is that described in EP 0368 864 B1. In this process (hereinafter referred to as "the Pearceprocess"), the raw whey is treated to reduce its specific gravity andionic strength to a level of not less than 25% of the original values.Either before or after the treatment, the pH is adjusted to between 3.8and 5.5 by the addition of acid. Next, the whey is heated to between 55°C. and 70° C. for at least 30 seconds to permit selective aggregation ofthe alpha-lactalbumin fraction. Thereafter, the whey is cooled to below55° C. for a time sufficient to permit flocculation of the aggregatedprotein and the flocculated alpha-lactalbumin is harvested. Thebeta-lactoglobulin remains soluble under the conditions used, along withother whey constituents such as lactose and can be recovered from themother liquor if required.

Another process for recovering purified protein fractions from whey hasbeen described by Amundson, C. H. et al, Journal of Food Processing andPreservation 6, 55-71, 1982. The Amundson process varies significantlyfrom the Pearce process in that it is the beta-lactoglobulin which isselectively precipitated, with the alpha-lactalbumin remaining insolution in the mother liquor. According to the Amundson process, rawwhey is treated to concentrate the protein while removing low molecularweight fractions such as water, minerals and lactose. The pH of theconcentrate is adjusted to 4.65, followed by a demineralisation step toremove low molecular weight ions, including calcium ions. The pH is thenreadjusted to 4.65. Under the conditions of pH and low ionic strengthused, the beta-lactoglobulin aggregates and can be separated as aprecipitate, leaving the alpha-lactalbumin in solution.

The present invention seeks to provide an efficient, integrated processfor treating whey for the recovery of its constituents, particularly asubstantially pure beta-lactoglobulin fraction, an enrichedalpha-lactalbumin fraction and lactose.

Accordingly, the present invention provides a process for the recoveryof whey constituents, comprising the steps of:

(a) reducing the mineral content of raw whey and in particular reducingthe calcium content to below 120 parts per million (p.p.m.) on a drymatter basis;

(b) reducing the pH of the whey to between 1.8 and 3.4;

(c) heating the whey to between 71° C. and 98° C. for between 50 secondsand 95 seconds, followed by rapid cooling to about 10° C.;

(d) concentrating the whey to between 55% and 63% total solids at atemperature not exceeding 69° C.;

(e) cooling the whey for a period of time and at a temperaturesufficient to permit crystallisation of lactose from the whey;

(f) separating the resulting lactose crystals from the remaining wheyprotein liquor;

(g) adjusting the pH of the whey protein liquor to a pH of between 4.3and 4.7 at a temperature of less than 10° C. and then heating to atemperature of between 35° C. and 54° C. for between 1 and 3 hours;

(h) separating the resultant flocculant comprising enrichedalpha-lactalbumin from the whey protein liquor comprising substantiallypure beta-lactoglobulin; and

(i) purifying the alpha-lactalbumin enriched flocculant by washing witha solution isoionic with the whey protein liquor, adjusting to a pH ofbetween 4.3 and 4.7 and refractionating the alpha-lactalbumin bycentrifugation or filtration.

The beta-lactoglobulin fraction can be further concentrated byultrafiltration, giving a beta-lactoglobulin retentate and a permeate.

In a preferred process, the steps (a) and (b) are carried out using acombination of electrodialysis and cation exchange. This allows the pHto be reduced to the required value with or without the direct additionof acid and the cation concentration to be reduced to the requiredlevel. Preferably, the pH is adjusted to between 1.8 and 2.2. Steps (a)and (b) may be carried out simultaneously.

The concentration of the whey may be carried out in a two stage process,the first stage being a concentration at less than 70° C. to between 20%and 35% total solids content and the second stage being effected at 64°C. or less to achieve a total solids content of between 55% and 63%, thefirst stage concentration being achieved by evaporation or by use ofmembranes and evaporation, the second stage being effected byevaporation.

Optionally, a further demineralisation step or steps may be undertakenafter the first concentration stage and before the second concentrationstage to reduce further the amount of phosphate present.

After the heat conditioning step (c), the proteins in the whey remain ina soluble state and accordingly, in step (f) the lactose can be removedby crystallisation and mechanical separation without taking with itthese proteins. After removal of the lactose crystals, the remainingwhey protein liquor typically contains between 31% and 45% protein on adry matter basis. The preferred temperature range for flocculating thealpha-lactalbumin component of this whey liquor at step (g) is between35° C. and 54° C. Most preferably, step (g) is conducted at temperatureof 52°+/-2° C.

After fractionation of the alpha-lactalbumin from thebeta-lactoglobulin, both products may be subjected to further downstreamprocesses, including defatting, neutralisation, concentration and/orspray drying.

In the process of the invention, raw whey is treated partially todemineralise it and the pH is adjusted to 3.4 or less. While the pHadjustment may be at least partially achieved by the addition of acid,in a preferred process the pH reduction is brought about by cationexchange without the addition of acid. The whey may be cheese whey, acidor rennet casein whey. Next, the whey undergoes a high temperaturetreatment, at between 71° C. and 98° C. At this temperature and underthe prevalent ionic conditions, the beta-lactoglobulin remains insolution, while the alpha-lactalbumin undergoes a change whichnevertheless results in no flocculation of the alpha-lactalbumin proteinmolecules. Next the whey is cooled and concentrated, after which lactosecrystals are permitted to grow at the lower temperatures. The crystalsare collected, and the whey protein liquor, containing thealpha-lactalbumin and beta-lactoglobulin both in a soluble state, isretained. In the next step, the whey protein liquor is adjusted tobetween pH 4.3 and 4.7 and heated to between 35° C. and 54° C., underwhich conditions the alpha-lactalbumin flocculates. This flocculationallows alpha-lactalbumin to be separated from soluble beta-lactoglobulinby mechanical separation which results in an enriched alpha-lactalbuminstream and a substantially pure beta-lactoglobulin stream.

The process will now be described in more detail with reference to theaccompanying drawings in which:

FIG. 1 shows a flow sheet representing an exemplary process according tothe invention; and

FIG. 2 is a chromatogram showing recovery of beta-lactoglobulin.

Referring to FIG. 1, raw whey is treated to reduce its mineral content,specifically, the calcium ions are reduced to less than 120 p.p.m. on adry matter basis. The demineralisation is preferably achieved byelectrodialysis and ion exchange, which has the advantage that at thesame time as removing the ions, the pH can be reduced to below 3.5 andpreferably to the desired point within the range of between 1.8 and 2.2.Using standard electrodialysis, up to 70% of the requireddemineralisation can be achieved. Then, a cation exchanger is used toremove sodium, potassium, magnesium and particularly calcium.

Next, the whey is subjected to a heat treatment at a temperature ofbetween 71° C. and 98° C. for between 50 seconds and 95 seconds. Due tothe low pH, the beta-lactoglobulin remains substantially soluble duringthe high temperature step. The very low calcium ion concentrationcombined with the heat treatment has the effect of inducing change inthe alpha-lactalbumin fraction without promoting the aggregation ofprotein. Thus, after the heat treatment step, the whey proteins exist assubstantially soluble protein.

In the next step, the temperature is reduced rapidly to below 10° C.,after which the whey is concentrated to between 55% and 63% totalsolids. Conveniently, the concentration is achieved in two stages. Inthe first stage, the temperature is raised to not greater than 70° C.and the solids content of the whey is increased to between 20% and 35%.Then, in the second stage, at a temperature of not more than 64° C., thetotal solids content is further increased to between 55% and 63%. Theconcentration may be achieved by any standard means used in the art, forexample by evaporation.

After the first stage of the concentration, additional electrodialysisand/or other demineralisation steps may be optionally conducted toremove other components such as phosphates.

Following concentration, the temperature of the whey is reduced from 64°C. to about 10° C. and the growth of lactose crystals is promoted. Oncethe crystallisation is complete, the lactose crystals are separated fromthe whey by mechanical separation, leaving the whey proteins in the wheyprotein liquor. The lactose prepared by this process is typically highquality lactose. For example, the quality obtained is usuallysufficiently high for the lactose to be saleable as "refined edible"grade lactose.

At this stage, the whey protein liquor contains between 31% and 45%protein on a dry matter basis.

Finally, the alpha-lactalbumin and beta-lactoglobulin fractions areseparated from one another. This is achieved by adjusting the pH of thewhey protein liquor to between 4.3 and 4.7 at less than 10° C., thenheating the whey protein liquor to between 35° C. and 54° C., preferablyabout 52°+/-2° C. and holding at that pH and temperature for a period ofat least one hour. The flocculant is separated mechanically or bymembrane separation from the remaining mother liquor to give an enrichedalpha-lactalbumin fraction. The mother liquor contains solublebeta-lactoglobulin in a substantially pure form. In down-streamprocessing steps, the alpha-lactalbumin fraction may be washed bymechanical means and/or by membrane diafiltration systems, and bothalpha-lactalbumin and beta-lactoglobulin fractions may be concentratedby ultrafiltration. The fat content of each product can be reduced bymechanical separation and/or microfiltration. Finally, the products areneutralised by the addition of base and spray dried.

The following non-limiting examples are given by way of illustration ofprocesses within the scope of the invention.

EXAMPLE 1

4000 litres of clarified acid casein whey was demineralised usingcommerically available electrodialysis and ion-exchange equipment. Thecombined demineralisation resulted in a product depleted in calcium, toless than 120 p.p.m. on a dry matter basis. In this demineralisationsystem the pH was reduced to 2.0. The product was then heat treated at atemperature of 94°+/-1° C. for a period of 60 seconds followed by rapidcooling to 10° C. prior to concentration in two stages, firstly to 22%total solids at a maximum temperature of 69° C. and finally to 62% totalsolids at a maximum temperature of 63° C. Lactose crystallisation wasachieved by means of controlled cooling. Lactose crystals were removedby mechanical separation leaving a concentrated whey protein liquorcontaining 37% protein on a dry matter basis.

The concentrated whey protein solution was adjusted to a pH of 4.45 at8° C., then heated to 53°+/-1° C. and held in a conditioning vessel atthat temperature for a minimum of 1 hour. All the concentrated wheyprotein had been removed from the conditioning vessel after the elapseof 3 hours. Holding under these conditions promoted selectiveflocculation of alpha-lactalbumin. The whey protein liquor was separatedusing a centrifugal separation which resulted in two streams, a heavyphase containing an enriched flocculation of alpha-lactalbumin and alight phase comprising a highly pure beta-lactoglobulin solution with noother major whey protein fractions present. FIG. 2a shows a chromatogramof a beta-lactoglobulin sample standard (SIGMA CHEMICAL COMPANY), whileFIG. 2b is a chromatogram of the beta-lactoglobulin fraction obtainedfrom this Example, and Table 1 details the peaks obtained from thisfraction.

                  TABLE 1                                                         ______________________________________                                        MAJOR HPLC FEATURES                                                           Peak Retention             Proportion of                                      Time (min)    Peak Identification                                                                        Total, %                                           ______________________________________                                        9-10, 23-25   Casein derived                                                                             5.4                                                              peptides                                                        19-20         beta-lactoglobulin                                                                         94.6                                               ______________________________________                                    

The alpha-lactalbumin enriched fraction was further purified by a seriesof washings using a solution isoionic with the whey protein liquor, pHadjustment to pH 4.45 and refractionation by centrifugal separationgiving a final alpha-lactalbumin enriched fraction.

The two protein streams were further concentrated using ultrafiltration.

Fat concentrations were reduced using mechanical separation andmicrofiltration.

The final beta-lactoglobulin product was neutralised with a combinationof KOH, NaOH, Mg(OH)₂ and Ca(OH)₂, concentrated to 20% total solids andspray dried.

The final alpha-lactalbumin product was neutralised with a combinationof KOH, NaOH, Mg(OH)₂ and Ca(OH)₂, concentrated to 20% total solids andspray dried.

EXAMPLE 2

4000 litres of cheddar cheese whey was clarified and used as the rawmaterial. The process was then as in Example 1.

EXAMPLE 3

4000 litres of clarified rennet casein whey was used as the rawmaterial. The process was then as in Example 1.

EXAMPLE 4

In this example, the process was undertaken as in Examples 1, 2 and 3but included an additional demineralisation step when the product was at22% total solids. This demineralisation step was included to reducefurther the phosphate levels. The product was then concentrated to 62%total solids at 63°+/-1° C. and the process proceeded as in Examples 1,2 and 3.

EXAMPLE 5

In this example, the process was undertaken as in Examples 1, 2 and 3.However, the beta-lactoglobulin fraction was diafiltrated to 75% proteinon a dry matter basis, concentrated to 20% total solids, neutralisedwith a combination of KOH, NaOH, Mg(OH)₂ and Ca(OH)₂ and dried.

EXAMPLE 6

In this example the process was undertaken as in Examples 1, 2 and 3.However, the alpha-lactalbumin fraction was enriched by a combination ofwashing and ultrafiltration to 65% protein on a dry matter basis,concentrated to 22% total solids, neutralised with a combination of KOH,NaOH, Mg(OH)₂ and Ca(OH)₂.

It will of course be understood that the invention is not limited to thespecific details described herein, which are given by way of exampleonly, and that various modifications and alterations are possible withinthe scope of the invention as defined in the appended claims.

We claim:
 1. A process for the recovery of whey constituents, comprising the steps of(a) reducing the calcium content to below 120 parts per million (p.p.m.) on a dry matter basis; (b) reducing the pH of the whey to between 1.8 and 3.4; (c) heating the whey to between 71° C. and 98° C. for between 50 seconds and 95 seconds, followed by rapid cooling to about 10° C.; (d) concentrating the whey to between 55% and 63% total solids at a temperature not exceeding 69° C.; (e) cooling the whey for a period of time and at a temperature sufficient to permit crystallisation of lactose from the whey; (f) separating the resulting lactose crystals from the remaining whey protein liquor; (g) adjusting the pH of the whey protein liquor to a pH of between 4.3 and 4.7 at a temperature of less than 10° C. and then heating to a temperature of between 35° C. and 54° C. for between 1 and 3 hours; (h) separating the resultant flocculant comprising enriched alpha-lactalbumin from the whey protein liquor comprising substantially pure beta-lactoglobulin; and (i) purifying the alpha-lactalbumin enriched flocculant by washing with a solution isoionic with the whey protein liquor, adjusting to a pH of between 4.3 and 4.7 and refractionating the alpha-lactalbumin by centrifugation or filtration.
 2. A process according to claim 1, in which the pH is reduced in step (b) to between 1.8 and 2.2.
 3. A process according to claim 1, in which steps (a) and (b) are carried out simultaneously by a combination of electrodialysis and cation exchange.
 4. A process according to claim 1, in which the concentration step (d) is carried out in two stages, the first stage comprising concentrating the whey to between 20% and 35% total solids content at a temperature less than 70° C. and the second stage comprising concentrating to a total solids content of between 55% and 63% at a temperature no greater than 64° C.
 5. A process according to claim 4, in which the first concentration stage is effected by evaporation or by the combined use of membranes and evaporation and the second concentration stage is effected by evaporation.
 6. A process according to claim 4, in which an additional electrodialysis and/or demineralisation step is carried out between the two concentration stages.
 7. A process according to claim 1, in which step (g) is carried out at 52° C.±2° C.
 8. A process according to claim 1, in which the lactose crystals are separated from the whey protein liquor by mechanical separation.
 9. A process according to claim 1, in which the resultant alpha-lactalbumin or beta-lactoglobulin product is subjected to any of defatting, neutralisation, concentration and/or spray drying. 